<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>外部引入</title>
</head>
<body>
    <button id="btn">按钮（李易峰）</button>
    <!-- 
        1、关键词script，属性src 
        2、创建外部脚本文件--demo.js，注意文件名是dmeo，后缀是js
        3、引入外部脚本，语法<script src="脚本路径"></script>
    -->
    <script src="./demo.js"></script>
</body>
</html>